Calculate Amp Capacity?

How do I calculate the amp capacity of a circuit that splits?

For example:

Battery > 1 foot of 10awg > splice/split into two legs of 10awg 10 feet long

How do I calculate how many amps each leg can carry?

I use wirebarn for 1:1 circuits but am unsure if I calculate each section separately or what.

I think you'll be limited by the 10 ft run which can carry around 25-30 amps. The one foot piece of 10awg should be able to carry more than the 50amps that the 2 - 10' pieces put together can draw. Just an opinion though.
I would just run 2 - 11' 10awg and not worry about it.

Thanks for the reply.
That's what I settled on as I didn't find much (or didn't use the correct search terms) online but it makes logical sense. This is being used for 55w lights so it is really just a curiosity thing.
I agree using 2 runs would be easiest but I didn't want to use another relay when the load didn't really call for it. Not that it calls for 10awg either but...

It’ll depend upon the capacity of that particular wire. Not all wires of the same gauge can handle the same current, even if you are comparing an oxygen free copper wire to another OFC wire.

Each 10’ section will receive half the current they are rated for. There’s not a huge difference between what can be handled at 1’ and 10’. Again, depending upon the wire.

You could use a 6-12” section of similar 8 gauge (you might have to go with 4awg depending upon the wire) then split down to 10awg to get both 10’ sections at Max capacity or just run 2 11’ 10awg leads.

Thanks gbloes. Due to the relay I am using, the largest I can get in the terminal (MP280) is a 10awg txl. So while I could do two relays, my current load doesn't justify that.
Do you know if there is a calculation for this or is it just a matter of calculating each piece (3) separately and using the lowest capacity as the max?